Communication devices such as wireless communication devices, that simply may be named wireless devices, may also be known as e.g. User Equipments (UEs), mobile terminals, wireless terminals and/or Mobile Stations (MS). A wireless device is enabled to communicate wirelessly in a wireless communication network that typically is a cellular communications network, which may also be referred to as a wireless communication system, or radio communication system, sometimes also referred to as a cellular radio system, cellular network or cellular communication system. A wireless communication network may sometimes simply be referred to as a network and abbreviated NW. The communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN) and possibly one or more Core Networks (CN), comprised within the wireless communication network. The wireless device may further be referred to as a mobile telephone, cellular telephone, laptop, Personal Digital Assistant (PDA), tablet computer, just to mention some further examples. Wireless devices may be so called Machine to Machine (M2M) devices or Machine Type Communication (MTC) devices, i.e. a device that is not necessarily associated with a conventional user, such as a human, directly using the device. MTC devices may be as defined by 3GPP.
The wireless device may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data, via the RAN, with another entity, such as another wireless device or a server.
The cellular communication network covers a geographical area which is divided into cell areas, wherein each cell area is served by at least one base station, or Base Station (BS), e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell may be typically identified by one or more cell identities. The base station at a base station site provides radio coverage for one or more cells. A cell is thus associated with a geographical area where radio coverage for that cell is provided by the base station at the base station site. Cells may overlap so that several cells cover the same geographical area. By the base station providing or serving a cell is meant that the base station provides radio coverage such that one or more wireless devices located in the geographical area where the radio coverage is provided may be served by the base station in said cell. When a wireless device is said to be served in or by a cell this implies that the wireless device is served by the base station providing radio coverage for the cell. One base station may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the wireless device within range of the base stations.
In some RANs, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunication System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communication (originally: Groupe Spécial Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or eNBs, may be directly connected to other base stations and may be directly connected to one or more core networks.
UMTS is a third generation mobile communication system, which may be referred to as 3rd generation or 3G, and which evolved from the GSM, and provides improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for wireless devices.
General Packet Radio Service (GPRS) is a packet oriented mobile data service on the 2G cellular communication system's global system for mobile communications (GSM).
Enhanced Data rates for GSM Evolution (EDGE) also known as Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC), or Enhanced Data rates for Global Evolution is a digital mobile phone technology that allows improved data transmission rates as a backward-compatible extension of GSM.
High Speed Packet Access (HSPA) is an amalgamation of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), defined by 3GPP, that extends and improves the performance of existing 3rd generation mobile telecommunication networks utilizing the WCDMA. Such networks may be named WCDMA/HSPA.
The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies, for example into evolved UTRAN (E-UTRAN) used in LTE.
The expression downlink, which may be abbreviated DL, is used for the transmission path from the base station to the wireless device. The expression uplink, which may be abbreviated UL, is used for the transmission path in the opposite direction i.e. from the wireless device to the base station.
Machine Type Communication (MTC) has in recent years, especially in the context of the Internet of Things (IoT), shown to be a growing market segment for cellular technologies. An MTC device may be a communication device, typically a wireless communication device or simply wireless device, that is a self and/or automatically controlled unattended machine, and that is typically not associated with an active human user in order to generate data traffic. An MTC device may be understood to be typically more simple, and typically associated with a more specific application or purpose, than and in contrast to a conventional mobile phone or smart phone. MTC involves communication in a wireless communication network to and/or from MTC devices, which communication typically is of quite different nature and with other requirements than communication associated with e.g. conventional mobile phones and smart phones. In the context of and growth of the IoT it is evidently so that MTC traffic will be increasing and thus needs to be increasingly supported in wireless communication systems.
A general problem related to (re)using existing technologies and systems is that the requirements for the new type of devices are typically different than conventional requirements, e.g. regarding the type and amount of traffic, performance etc. Existing systems have not been developed with these new requirements in mind. Also, traffic generated by new type of devices will typically be in addition to conventional traffic already supported by an existing system, which existing traffic may typically need to continue to be supported by and in the system, preferably without any substantial disturbance and/or deterioration of already supported services and performance.
Any need of modifications of existing systems and technology may benefit from being cost efficient, such as enabled by low complexity modifications, and preferably allowing legacy devices, i.e. devices already being employed, to continue to be used and co-exist with the new type of devices in one and the same wireless communication system.
At the meeting RAN #72, a Work item on “Positioning Enhancements for GERAN” was approved, see e.g. RP-161260, “New Work Item on Positioning Enhancements for GERAN”, Ericsson L M, Orange, MediaTek Inc., Sierra Wireless, Nokia, RAN #72. One candidate method for realizing improved accuracy when determining the position of a MS (mobile station) is TA (timing advance) multilateration, which relies on establishing the MS position based on TA values in multiple cells. See e.g. RP-161034, “Positioning Enhancements for GERAN—introducing TA trilateration”, Ericsson L M, RAN #72.
At RAN1#86, a proposal based on a similar approach was made also to support positioning of Narrow Band IoT (NB-IoT) mobiles.
TA is a measure of the propagation delay between a BTS (base transceiver station) and the MS, and since the speed by which radio waves travel is known, the distance between the BTS and the MS may be derived. Further, if the TA applicable to a MS is measured within multiple BTSs and the positions of these BTSs are known, the position of the MS may be derived using the measured TA values. Measurement of TA may require that the MS synchronizes to each neighbor BTS, and transmits a signal time-aligned with the estimated timing of the downlink channel received from each BTS. The BTS measures the time difference between its own time reference for the downlink channel, and the timing of the received signal (transmitted by the MS). This time difference is equal to two times the propagation delay between the BTS and the MS (one propagation delay of the BTS's synchronization signal sent on the downlink channel to the MS, plus one equal propagation delay of the signal transmitted by the MS back to the BTS).
Once the set of TA values are established using a set of one or more BTS during a given positioning procedure, the position of the device may be derived through so called Multilateration, wherein the position of the device may be determined by the intersection of a set of hyperbolic curves associated with each BTS, see e.g. FIG. 1. FIG. 1 schematically illustrates Multilateration involving three base stations associated with three timing advance values for a particular device: values TA1, TA2 and TA3. The calculation of the position of the device may be typically carried out by the serving positioning node, i.e., the Serving Mobile Location Center (SMLC), which implies that all of the derived timing advance and associated BTS position information may need to be sent to the positioning node that initiated the positioning procedure, i.e., the serving SMLC. The BTS used during a given positioning procedure may fall into one of the following categories: foreign BTS, local BTS, and serving BTS.
A Foreign BTS may be understood as a BTS associated with a Base Station Subsystem (BSS) that uses a positioning node that is different from the positioning node used by the BSS that manages the cell serving the MS when the positioning procedure is initiated. In this case, the derived timing advance information and identity of the corresponding cell may be relayed to the serving positioning node using the core network, i.e., in this case the BSS has no context for the MS. A context may be understood as information provided to a BSS by the positioning node prior to the positioning node initiating a positioning procedure for a given MS, wherein the BSS manages the cell in which the MS is currently located and wherein the positioning node requests the BSS to begin the positioning procedure for the MS subsequent to providing the BSS with the information used for context establishment. This context information may consist of the logical connection established between the serving BSS and positioning node established as a result of the serving BSS sending a BSSMAP-LE Perform Location Request message, e.g., as defined in 3GPP TS 49.031 v13.0.0, to the positioning node and/or as a result of the serving BSS sending a BSSMAP-LE Assistance Information Request message, e.g., as defined in 3GPP TS 49.031 v13.0.0, to the positioning node after the logical connection has been established.
A Local BTS may be understood as a BTS associated with a BSS that uses the same positioning node as the BSS that manages the cell serving the MS when the positioning procedure is initiated. In this case, the derived timing advance information and identity of the corresponding cell may be relayed to the serving positioning node using the core network, i.e., in this case the BSS has no context for the MS.
A Serving BTS may be understood as a BTS associated with a BSS that manages the cell serving the MS when the positioning procedure is initiated. In this case, the derived timing advance information and identity of the corresponding cell are sent directly to the serving positioning node, i.e., in this case the BSS has a context for the MS.
Multilateration may be particularly useful for Cellular IoT devices since such devices may be subject to movement and expected to provide information for which corresponding location information may be useful. It is expected that in a near future, the population of Cellular IoT devices will be very large. Various predictions exist that assumes >60000 devices per square kilometer, and even that assumes 1000000 devices per square kilometer. A large fraction of these devices are expected to be stationary, e.g., gas and electricity meters, vending machines, etc.
EC-GSM-IoT and NB-IoT are two standards for supporting Cellular IoT devices that have been specified by 3GPP TSG GERAN and TSG RAN. Existing methods, however, do not fully support timing advance multilateration, when non-serving nodes are involved in the signalling, which may result in suboptimal location procedures and wasted energy, processing, and radio resources.